Walkthrough of an RPL program for an RPN programmer

[Albert Chan]

(08-19-2018 10:15 AM)Thomas Klemm Wrote:  I'm not aware of a way to partition a list in Python.
However we can use map with an additional copy of the list that is rotated by one place:

You mean like this ?

Code:

def partition(lst, n, step=0):    # no step = no overlap
    return [ lst[i-n:i] for i in range(n, len(lst) + 1, step or n) ]

Perhaps we do not need partitioned list, map, and sum. Just do it all at once.

Code:

def cross_and_sum(((x, y), sum), v):
    return v, sum + (x * v[1] - y * v[0])

def area(v):
    'Area of polygon using shoelace formula'
    _, s = reduce(cross_and_sum, v, (v[-1], 0))
    return 0.5 * abs(s)